2 * linux/arch/i386/kernel/ioport.c
4 * This contains the io-permission bitmap code - written by obz, with changes
8 #include <linux/sched.h>
9 #include <linux/kernel.h>
10 #include <linux/errno.h>
11 #include <linux/types.h>
12 #include <linux/ioport.h>
14 #include <linux/smp.h>
15 #include <linux/smp_lock.h>
16 #include <linux/stddef.h>
18 /* Set EXTENT bits starting at BASE in BITMAP to value TURN_ON. */
19 static void set_bitmap(unsigned long *bitmap, short base, short extent, int new_value)
22 unsigned long *bitmap_base = bitmap + (base >> 5);
23 unsigned short low_index = base & 0x1f;
24 int length = low_index + extent;
27 mask = (~0 << low_index);
29 mask &= ~(~0 << length);
31 *bitmap_base++ |= mask;
33 *bitmap_base++ &= ~mask;
37 mask = (new_value ? ~0 : 0);
38 while (length >= 32) {
39 *bitmap_base++ = mask;
44 mask = ~(~0 << length);
46 *bitmap_base++ |= mask;
48 *bitmap_base++ &= ~mask;
53 * this changes the io permissions bitmap in the current task.
55 asmlinkage int sys_ioperm(unsigned long from, unsigned long num, int turn_on)
57 struct thread_struct * t = ¤t->thread;
58 struct tss_struct * tss = init_tss + smp_processor_id();
60 if ((from + num <= from) || (from + num > IO_BITMAP_SIZE*32))
62 if (turn_on && !capable(CAP_SYS_RAWIO))
65 * If it's the first ioperm() call in this thread's lifetime, set the
66 * IO bitmap up. ioperm() is much less timing critical than clone(),
67 * this is why we delay this operation until now:
73 memset(t->io_bitmap,0xff,(IO_BITMAP_SIZE+1)*4);
78 * do it in the per-thread copy and in the TSS ...
80 set_bitmap(t->io_bitmap, from, num, !turn_on);
81 if (tss->bitmap == IO_BITMAP_OFFSET) { /* already active? */
82 set_bitmap(tss->io_bitmap, from, num, !turn_on);
84 memcpy(tss->io_bitmap, t->io_bitmap, IO_BITMAP_BYTES);
85 tss->bitmap = IO_BITMAP_OFFSET; /* Activate it in the TSS */
92 * sys_iopl has to be used when you want to access the IO ports
93 * beyond the 0x3ff range: to get the full 65536 ports bitmapped
94 * you'd need 8kB of bitmaps/process, which is a bit excessive.
96 * Here we just change the eflags value on the stack: we allow
97 * only the super-user to do it. This depends on the stack-layout
98 * on system-call entry - see also fork() and the signal handling
102 asmlinkage int sys_iopl(unsigned long unused)
104 struct pt_regs * regs = (struct pt_regs *) &unused;
105 unsigned int level = regs->ebx;
106 unsigned int old = (regs->eflags >> 12) & 3;
110 /* Trying to gain more privileges? */
112 if (!capable(CAP_SYS_RAWIO))
115 regs->eflags = (regs->eflags & 0xffffcfff) | (level << 12);